But on a recent evening, the Lawndale resident was standing with a group of children in a multipurpose room at the Lawndale Community Center.
Violin in hand, Velazquez guided the students through a performance in front of 300 parents and other community members.
It was another small step for a youth music program that continues to grow.
"It's not just about teaching kids music," Velazquez said on a recent afternoon in his office off Catalina Avenue in Redondo Beach.
Drawings from his two young children, Manolo and Camila, are taped to the walls. Black violin cases sit near the door.
Today, about 40 children and their parents participate in Planet Orchestra, a youth music program Velazquez started about two years ago with a shoestring budget and a simple goal -- to bring people together, through music.
"The goal is to learn to connect and harmonize," he said. "When everybody comes together to connect and push in the same direction, everybody wins."
Velazquez has emerged as a leader in Lawndale and has worked to be an advocate for children and their parents.
As a member of the city of Lawndale's Parks, Recreational and Social Services Commission, he's worked to create recreational opportunities for children and families stricken from abuse.
"You look at the void and see that nothing is getting done," Velazquez said. "I see that it has to be me."
Originally from Cuiliacan, a city in northwest Mexico, Velazquez came to the United States when he was 18.
He enrolled at El Camino College, where he was first introduced to the violin.
Although Velazquez eventually went on to study math at California State University, Dominguez Hills, the violin remained at his side.
"I thought, 'Where was this when I was a teenager?"' Velazquez said of the instrument that he taught his son to play. "I treasured it immediately."
But his work in the community transcends violin classes.
He's been on the front lines in the city's effort to combat graffiti, organizing groups of parents -- often from different cultures, speaking different languages -- and walking streets together near local elementary schools removing the spray-painted vandalism.
"Graffiti is a tragic manifestation of kids who are not well-served," Velazquez said. "These kids are not well-served by adults."
He's faced off against local school districts, leading an opposition movement against Measure CL, a parcel tax that created new funding for local school districts.
Velazquez saw the tax as an attack on local property and business owners that was based on flawed revenue numbers.
"Something like Measure CL is problematic on so many levels," said Velazquez, who debated school district officials and met with homeowner associations in the campaign to defeat Measure CL, which passed. "That most people don't see the demagoguery is very frustrating. It's education snake oil. And people buy it."
Velazquez, who is married with two young children, has played an active role in public schools, working to increase parent involvement in the classroom and with administrators. He's fought for students.
In 2010, he led efforts to keep a beloved principal from being involuntarily transferred to a new school. The effort ultimately failed, and the principal retired two years later.
"About six years ago, I bought into this idea that parent involvement turns things around," Velazquez said. "But little by little, I started learning how school districts are run. The different complexities. Children are totally ignored. I started to understand things that weren't supposed to be talked about."
Other Lawndale leaders have applauded Velazquez for his work.
"We don't have enough parents like Mariano," said Sandra Suarez, a former Centinela school board member who campaign with Velazquez against Measure CL. "There is not enough parent involvement. We need more people like him the community."
And his music program, perhaps the centerpiece of his volunteer work, continues to build on its success, attracting students and their families from across the South Bay.
"He's got energy, enthusiasm and ideas," Councilman Jim Osborne said. "And he's not afraid to take a stand."
In June, Velazquez joined the Lawndale Parks, Recreation and Social Services Commission, where he is working to build social programs and bring city officials, educators and law enforcement authorities together to support parents and their children.
That goal reflects the idea of Planet Orchestra, which was able to grow from a grass-roots, parent-led class to a nonprofit foundation with professional teachers assisted by community members, city officials, art foundations and generous donors.
He juggles his day job creating drafting models for homes and commercial areas with educating his children at home and volunteering in the community.
He has shied away from pleas to run for elective office, simply because he said it would limit him in his volunteer work. And there is much more to do.
"I can't imagine neglecting all the work that needs to be done," he said.